ABSTRACT The current study aimed to investigate the longitudinal reciprocal association of social participation and life satisfaction by considering the motivation for social participation as a moderating variable. The data from 4,007 Korean adults were analyzed. Motivation for social participation was categorized into autonomous motivation or controlled motivation. Multi-group autoregressive cross-lagged modeling revealed that life satisfaction and social participation showed reciprocal relationships only when adults have autonomous motivation during social engagement. Social participation with controlled motivation was associated with later lower life satisfaction. Additionally, prior life satisfaction was not associated with controlled social participation. The results showed that the reason people participate in social activity is critical in understanding the effect of social participation in adulthood. Active social engagement with autonomous motivation and disengagement from controlled social participation may be a critical key for life satisfaction.